/*
 * Copyright (c) 2018, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */
package com.oracle.svm.core.c;

import java.util.EnumSet;
import java.util.Optional;
import java.util.function.IntSupplier;
import java.util.function.Supplier;

import org.graalvm.nativeimage.Platform;
import org.graalvm.nativeimage.Platforms;
import org.graalvm.word.PointerBase;

import com.oracle.svm.core.graal.code.CGlobalDataInfo;

/**
 * Stores static information about a CGlobal. Build-specific information is stored in
 * {@link CGlobalDataInfo}. This separation of data is used to facilitate storing
 * {@link CGlobalDataImpl} within static fields.
 */
public final class CGlobalDataImpl<T extends PointerBase> extends CGlobalData<T> {

    /**
     * The name of the symbol to create for this data (or null to create no symbol), or if the other
     * fields are null, the name of the symbol to be referenced by this instance.
     */
    @Platforms(Platform.HOSTED_ONLY.class) //
    public final String symbolName;

    /**
     * When a CGlobal does not have a {@link #symbolName}, when building layered images,
     * {@link #computeCodeLocation} is used as a unique key.
     */
    @Platforms(Platform.HOSTED_ONLY.class) //
    public final StackWalker.StackFrame codeLocation;

    @Platforms(Platform.HOSTED_ONLY.class) //
    public final Supplier<byte[]> bytesSupplier;
    @Platforms(Platform.HOSTED_ONLY.class) //
    public final IntSupplier sizeSupplier;
    public final boolean nonConstant;

    @Platforms(Platform.HOSTED_ONLY.class)
    CGlobalDataImpl(String symbolName, Supplier<byte[]> bytesSupplier) {
        this(symbolName, bytesSupplier, null, false); // pre-existing data
    }

    @Platforms(Platform.HOSTED_ONLY.class)
    CGlobalDataImpl(String symbolName, Supplier<byte[]> bytesSupplier, boolean nonConstant) {
        this(symbolName, bytesSupplier, null, nonConstant);
    }

    @Platforms(Platform.HOSTED_ONLY.class)
    CGlobalDataImpl(String symbolName, IntSupplier sizeSupplier) {
        this(symbolName, null, sizeSupplier, false); // zero-initialized data
    }

    @Platforms(Platform.HOSTED_ONLY.class)
    CGlobalDataImpl(String symbolName) {
        this(symbolName, null, null, false); // reference to symbol
    }

    /**
     * nonConstant parameter marks whether object have to be used as a compile-time constant. If
     * nonConstant is 'false', the symbolName should be known at compile time.
     */
    @Platforms(Platform.HOSTED_ONLY.class)
    CGlobalDataImpl(String symbolName, boolean nonConstant) {
        this(symbolName, null, null, nonConstant);
    }

    @Platforms(Platform.HOSTED_ONLY.class)
    public boolean isSymbolReference() {
        return bytesSupplier == null && sizeSupplier == null;
    }

    @Platforms(Platform.HOSTED_ONLY.class)
    private CGlobalDataImpl(String symbolName, Supplier<byte[]> bytesSupplier, IntSupplier sizeSupplier, boolean nonConstant) {
        assert !(bytesSupplier != null && sizeSupplier != null);
        this.symbolName = symbolName;
        this.bytesSupplier = bytesSupplier;
        this.sizeSupplier = sizeSupplier;
        this.nonConstant = nonConstant;
        /*
         * Note the uniqueness of code locations is checked in
         * CGlobalDataFeature#createCGlobalDataInfo.
         */
        this.codeLocation = this.symbolName == null ? computeCodeLocation() : null;
    }

    /**
     * A CGlobal's code location is defined to be the caller of the {@link CGlobalDataFactory} used
     * to create the instance.
     */
    @Platforms(Platform.HOSTED_ONLY.class)
    private static StackWalker.StackFrame computeCodeLocation() {
        var walker = StackWalker.getInstance(EnumSet.of(StackWalker.Option.RETAIN_CLASS_REFERENCE));
        return walker.walk((stackStream) -> {
            Optional<StackWalker.StackFrame> result = stackStream.filter(stackFrame -> {
                var declaringClass = stackFrame.getDeclaringClass();
                return declaringClass != CGlobalDataImpl.class && declaringClass != CGlobalDataFactory.class;
            }).findFirst();
            return result.get();
        });
    }
}
